4 d BULLETIN 167, U. S. DEPARTMENT OF AGRICULTURE. 
~ mealworm (Yenebrio molitor L.), and a few others less common are 
particularly hard to kill when in the adult stage. The larve of the 
mealworms, Tenebrio molitor L., Tenebrio obscurus L., and closely 
allied species, are likewise found by experiment to possess great 
tenacity of life. It is therefore recommended that a proportionately 
larger amount of para-dichlorobenzene be used when combating these 
species. Moths, flies, roaches, ants, and aphides are readily killed 
by para-dichlorobenzene when used in the ordinary strength recom- 
mended under the heading ‘‘ Para-dichlorobenzene as an insecticide.” 
The action of para-dichlorobenzene on insects is primarily upon 
their nervous systems. This property is readily manifested when a 
moth is exposed to the vapors for a few seconds. It first displays 
great excitement and uneasiness, followed closely by spasmodic con- 
vulsions, and finally turns cver on its back. While in this position 
violent nervous and muscular reflex action is noticed until life is. 
extinct. 
The moths on which this gas has been tested include the Angoumois 
grain moth (Sztotroga cerealella Oliv.), Mediterranean flour moth 
(Ephestia kuehniella Zell.), Indian meal moth (Plodia interpunctella 
Hbn.), meal snout moth (Pyralis farinalis 1.), and the case-bearing 
clothes-moth (Tinea pellionella L.). 
EXPERIMENTS WITH PARA-DICHLOROBENZENE AS A FUMIGANT. 
During the spring of 1914, while stationed at Washington, D. C., 
the writer, working under the direction of Dr. F. H. Chittenden, per- 
formed a series of experiments with para-dichlorobenzene as a fumi- 
gant for stored-product insects. The chemical was first used on a small 
scale, and results were afterwards checked up in a specially con- 
structed air-tight fumigating box having a capacity of 100 cubic feet 
(Pl. I.) The average temperature was computed from the records of 
a thermograph placed in the box, and the para-dichlorobenzene 
exposed in shallow piepans or the tops of 5-gallon lard cans, since - 
these shallow receptacles present a much larger surface of the chemical 
for evaporation. These pans were placed about 4 feet above the 
material to be fumigated, which was contained in muslin bags of | 
variable capacity (see Pl. IZ) and which had previously been ascer- 
tained to be free from live insects. Into this material, consisting of 
wheat, cornmeal, flour, rice, and other cereals, were then introduced 
living insects, the number and species of each being recorded on an 
attached tag. 
The respective amounts of para-dichlorobenzene used in each 
experiment and the tabulated results follow. 
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